1. Field of the Invention
The present invention relates to a thin film magnetic head having at least an inductive-type magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
In recent years, performance improvement in thin film magnetic heads has been sought in accordance with an increase in surface recording density of a hard disk drive. A composite thin film magnetic head, which has a layered structure including a recording head having an inductive-type magnetic transducer for writing and a reproducing head having magneto resistive (MR) elements for reading, has been widely used as a thin film magnetic head.
The performance of the reproducing head can be improved in several ways. One way is to form an MR film from a material which has good magnetic resistive sensitivity such as a GMR film instead of an AMR film; another is to adjust a pattern width of the MR film, especially an MR height. The MR height is the length (height) between one end of the MR element closer to an air-bearing surface and the other end thereof. The MR height is originally determined by an amount of grinding when the air-bearing surface is processed. The air-bearing surface as used herein refers to a surface of a thin film magnetic head that faces a magnetic recording medium and is also called a track surface.
Performance improvement in a recording head has also been expected in accordance with the performance improvement in a reproducing head. A factor determining the performance of a recording head is the throat height (TH). The throat height is the length (height) of a portion (magnetic pole portion) spreading from the air-bearing surface to an edge of an insulating layer for electrically isolating a thin film coil for causing magnetic flux. Reducing the throat height is desirable in order to improve the performance of a recording head. The throat height is determined as well by an amount of grinding when the air-bearing surface is processed.
It is required to increase the track density of a magnetic recording medium in order to increase the recording density among the performance of a recording head. This requires a recording head having a narrow track structure in which the width of a bottom pole and a top pole sandwiching a write gap layer on the air-bearing surface is reduced to the order of some microns to submicron. Semiconductor process technique is used to achieve this narrow track structure.
FIGS. 21A and 21B show a structure of a composite thin film magnetic head as an example of a thin film magnetic head of a related art. FIG. 21A shows a cross section perpendicular to the air-bearing surface. FIG. 21B shows a cross section parallel to the air-bearing surface of the magnetic pole portion.
The composite thin film magnetic head has an insulating layer 102 made of, for example, alumina (aluminum oxide, Al2O3) of about 5 to 10 xcexcm in thickness formed on a substrate 101 made of, for example, aluminum oxide and titanium carbide (Al2O3.TiC). Further, a bottom shield layer 103 for a reproducing head is formed from a magnetic material on the insulating layer 102. Alumina or aluminum nitride, for example, is sputtered on the bottom shield layer 103 to form a bottom shield gap film 104 as an insulating layer. An MR element 105 for reproduction is formed on the bottom shield gap film 104. Furthermore, a pair of first electrode layer 106 which is electrically connected to the MR element 105 is formed on the bottom shield gap film 104. The first electrode layer 106 is formed by stacking TiW, CoPt, TiW, and Ta, for example.
Also, a pair of second electrode layer 107 is electrically connected to the first electrode layer 106. The second electrode layer 107 can be formed from copper (Cu), for example. The first electrode layer 106 and the second electrode layer 107 constitute a lead, which is electrically connected to the MR element 105.
As an insulating layer, an upper shield gap layer 108 is formed on the bottom shield gap layer 104 and the MR element 105. The MR element 105 is buried in the shield gap layers 104 and 108. A top shield-cum-bottom pole layer (called bottom pole layer in the following) 109, made of a magnetic material and used both for a reproducing head and for a recording head is formed on the upper shield gap layer 108. A write gap layer 110 made of an insulating film such as an alumina film is formed on the bottom pole layer 109. A photoresist layer 111 which determines throat height is formed on the write gap layer 110 in a predetermined pattern. A first layer of a thin film coil 112 for an inductive-type head for recording is formed on the photoresist layer 111. Further, a photoresist layer 113 is formed in a predetermined pattern on the photoresist layer 111 and the thin film coil 112. A heat treatment of the temperature of 200-250xc2x0 C., for example, is applied for stabilizing the photoresist layer 113. A second layer of a thin film coil 114 is formed on the photoresist layer 113. A photoresist layer 115, which is stabilized by heat treatment, is formed in a predetermined pattern on the photoresist layer 113 and the thin film coil 114.
The write gap layer 110 is etched partially to form a yoke in the rear (right-hand side in FIG. 21A) of the thin film coils 112 and 114. A top pole layer 116 made of a magnetic material for the recording head, that is, a high saturation flux density material such as permalloy (NiFe) or nitride ferrous (FeN) is formed on the write gap layer 110, the photoresist layers 111, 113, and 115. The top pole layer 116 has a contact with, and is magnetically coupled to the bottom pole layer 109 in the rear of the thin film coils 112 and 114. An over coat layer 117 made of alumina, for example, is formed on the top pole layer 116. Each of the side walls of a part of the top pole layer 116, the write gap layer 110 and the bottom pole layer 109 is formed vertically and in a self-aligned manner to form a trim structure. This trim structure can prevent widening of effective write track width caused by widening of magnetic flux in writing data in the narrow track.
FIG. 22 shows an example of a shape of the top pole layer 116. The top pole layer 116 has a magnetic pole portion 116a which is placed closer to the air-bearing surface 120 and a yoke area 116b which is placed at the position facing the thin film coils 112 and 114. A part of the yoke area 116b at the side of the magnetic pole portion 116a is tapered off as it is close to the magnetic pole portion 116a. The outer edge of the tapered part is inclined to 45xc2x0, for example, against the surface which is parallel to the air-bearing surface 120. The TH0, Throat Height position 0, in figures indicates a position of the edge of the insulating layer closer to the air bearing surface, which separates thin film coil electrically.
These days, reducing the write track width, or the width of the magnetic pole portion (called pole width in the followings), is required for high surface density writing. FIG. 23 shows an example of a shape of the top pole layer 116 with narrower pole width than that of FIG. 22. In this example, the width of the magnetic pole portion 116a is 0.8-1.2 xcexcm. It is possible that the width of the magnetic pole portion 116a will be around 0.4 xcexcm of the submicron order in future.
Conventionally, if the top pole layer 116 is formed like that in FIG. 22, the magnetic flux caused from the thin film coils 112 and 114 does not saturate on the way but reaches to the top of the magnetic pole portion.
However, as shown in FIG. 23, for example, when the pole width is reduced, the flux saturates in vicinity of the Throat Height 0 position, TH0, and the flux does not reach to the top of the magnetic pole portion. As a result, an over write characteristic, that is, a characteristic in over-writing data on a recording media on which something is written already, indicates values as low as around 10-20 dB, for example, and the sufficient over write characteristic can not be obtained.
Meanwhile, the top pole layer is formed by the frame plating method, for example, described in Japanese Patent Application laid-down in Hei 7-262519. In order to form the top pole layer by the frame plating method, first, a thin electrode film made of permalloy, for example, is formed by sputtering, for example, all over the apex area which is a coil portion formed into a shape like a mountain. Next, photoresist is applied thereon and patterned through photolithography. A frame for plating is thus formed. Further, the top pole layer is formed through the plating method, using the electrode film formed earlier as a seed layer.
However, the apex area and other areas have, for example, equal to or more than 7 to 10 xcexcm differences in heights. The photoresist of 3-4 xcexcm in thickness is applied on the apex area. If the film thickness of the photoresist on the apex area is required to be equal to or more than 3 xcexcm, a photoresist film of equal to or more than 8 to 10 xcexcm, for example, in thickness is formed in the lower part of the apex area since the photoresist gathers into a lower area because of liquidity.
To form a narrow magnetic pole portion, a frame pattern with width of around 1.0 xcexcm each must be formed with a photoresist film. In other words, a micro pattern with width of 1.0 xcexcm or less must be formed with a photoresist film of 8-10 xcexcm or more in thickness. However, it has been extremely difficult to form such a thick photoresist pattern with a small width in manufacturing.
Further, during an exposure of photolithography, a light for the exposure is reflected by a bottom electrode film as a seed layer, and the photoresist is exposed also by the reflection light causing deformation of the photoresist pattern so that a sharp and accurate photoresist pattern can not be obtained. As a result, the top pole layer can not be formed in a desired shape; the side walls of the top pole layer take a shape of being rounded, for example. This is the case in particular when the top pole layer 116 is formed in the shape of that shown in FIG. 23. The reflection lights reflected by the bottom electrode film impinge in the vicinity of the border of the magnetic pole portion 116a and the yoke area 116b. These reflection lights include not only the light in the vertical direction but also the light reflected from the slope of the apex area in the diagonal or horizontal direction. The reflection lights affect on the exposure of the photoresist layer, and it easily allows a wider photoresist pattern than that with the desired value, which determines pole width.
The invention is presented to solve these problems. The first object is to provide a thin film magnetic head, which can obtain a sufficient over write characteristic even if pole width is reduced, and a method of manufacturing the same.
In addition to the first objective, the second object is to provide a thin film magnetic head, which can precisely control the pole width even if pole width is reduced, and a method of manufacturing the same.
A thin film magnetic head of the invention comprises an inductive-type magnetic transducer for writing which has two magnetic layers and a thin film coil provided between the magnetic layers with an insulating layer in between, the magnetic layers including two magnetic pole portions which are magnetically coupled to and face each other in part of the sides facing a recording medium with a write gap layer in between and comprise at least one layer for each magnetic layer, wherein at least one of the two magnetic layers comprising: a magnetic pole portion, one edge of which is placed closer to the surface facing the medium which face a recording medium; a submagnetic pole portion, one edge of which is magnetically coupled to the other edge of the magnetic pole portion, having a greater film thickness than that of the magnetic pole portion; and a yoke area being magnetically coupled to another edge of the sub-magnetic pole portion.
According to the invention, a manufacturing method of a thin film magnetic head comprising an inductive-type magnetic transducer for writing which has two magnetic layers and a thin film coil provided between the magnetic layers with an insulating layer in between, the magnetic layers including two magnetic pole portions which are magnetically coupled to and face each other in part of the sides facing a recording medium with a write gap layer in between and comprise at least one layer for each magnetic layer, comprises steps of: forming a magnetic pole portion so that one edge of the magnetic pole portion is placed closer to the surface facing the medium which faces the recording medium; forming an sub-magnetic pole portion, one edge of which is magnetically coupled to the other edge of the magnetic pole portion, having a greater film thickness than that of the magnetic pole portion; and forming a yoke area being magnetically coupled to another edge side of the sub-magnetic pole portion.
In the thin film magnetic head and the method of manufacturing the same of the invention, a sub-magnetic pole portion having a greater film thickness than that of the magnetic pole portion is magnetically coupled to the other edge of the magnetic pole portion. Therefore, it is possible to obtain a large volume of pole in vicinity of the throat height 0 position even if the width of the magnetic pole portion, or the pole width is reduced. Also, it is possible to suppress flux saturation in vicinity of the throat height 0 position and to obtain submicron order of pole width.
Further, in the thin film magnetic head and the manufacturing the same of the invention, the sub-magnetic pole portion may be wider than the magnetic pole portion.
Further, in the thin film magnetic head and the manufacturing the same of the invention, the magnetic pole portion may be formed to be vertical to the surface facing the medium and to the edge surface closer to the surface facing the medium of the sub-magnetic pole portion.
Further, in the thin film magnetic head and the manufacturing the same of the invention, at least the film thickness of the sub-magnetic pole portion may be formed to be reduced gradually as it is closer to the surface facing the medium.
Further, in the thin film magnetic head and the manufacturing the same of the invention, after the magnetic pole portion is formed as a magnetic layer with a rectangular section, the sub-magnetic pole portion may be formed by covering a part opposite to the surface facing the medium of the magnetic layer with at least one layer of other magnetic layers.
Further, in the thin film magnetic head and the manufacturing the same of the invention, after the gap layer is formed, an insulating layer for determining a throat height may be formed between the gap layer and the sub-magnetic pole portion of one of the magnetic layers.
Further, in the thin film magnetic head and the manufacturing the same of the invention, the edge closer to the surface facing the medium of the sub-magnetic pole portion may be placed in vicinity of the edge closer to the surface facing the medium of the insulating layer.
Further, in the thin film magnetic head and the manufacturing the same of the invention, it is preferable that the yoke area be formed wider than the sub-magnetic pole portion.
Further, in the thin film magnetic head and the manufacturing the same of the invention, at least one layer of thin film coil may be formed in a region spreading over the surface opposite to the surface facing the medium of the sub-magnetic pole portion and the surface of the gap layer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.